Identification and functional caracterization of novel lipases/acyltransferases of yeasts

• Main Author: Neang, Pisey
• Other Authors: Montpellier, SupAgro, Dubreucq, Eric, Subileau, Maëva
• Format: Thesis
• Language: French
• Published: 2013
• Subjects: Lipase/acyltransférase; Candida parapsilosis; Candida tropicalis; Candida viswanathii; Biocatalyse; Milieu biphasique aqueux; Biocatalysis; Biphasic aqueous medium; geo; envir; Antarc*; Antarctica
• Online Access: http://www.theses.fr/2013NSAM0005/document

Lipases/acyltransferases have intermediate properties between lipases and acyltransferases. Although being active hydrolases, they catalyze acyltransfer reactions preferentially to hydrolysis even in an aqueous medium with a high thermodynamic activity of water in the presence of various nucleophiles. Searching for new lipases/acyltransferases, either secreted by wild yeast strains or identified in protein sequences databases, allowed us to identify two new enzymes of this type: CvisL2 from Candida viswanathii and CtroL4a from C. tropicalis. The latter, produced by heterologous expression, has been more particularly studied and compared with the two already known, closely related, lipases/acyltransferases, CpLIP2 from C. parapsilosis and CaLIP4 from C. albicans, and with two more distantly related lipases (a new lipase AflaL0a from Aspergillus flavus and CaLA from C. antarctica, with 35 % and 31 % identity with CpLIP2, respectively). The specific catalytic behavior of the acyltransferases seems to be associated with sequence homology and phylogenetic relationships. Indeed, the three lipases/acyltransferases studied are part of a phylogenetic subgroup composed of various proteins (identity with CpLIP2 higher than 57 %), currently not characterized. Besides their acyltransfer activity, these new biocatalysts differ in properties such as their substrate selectivity, their stability in the presence of high alcohol concentration or their activity at low temperature, opening the way to new applications. Les lipases/acyltransférases présentent des propriétés intermédiaires entre les lipases et les acyltransférases. Capables de se comporter comme des hydrolases, elles catalysent cependant la réaction de transfert d'acyle préférentiellement à l'hydrolyse même en milieu aqueux à forte activité thermodynamique de l'eau en présence de divers nucléophiles. La recherche de nouvelles lipases/acyltransférases, soit sécrétées par des levures sauvages, soit identifiées parmi les séquences protéiques disponibles dans des bases ...